Illumination assembly including wavelength converting material having spatially varying density

ABSTRACT

Illumination assemblies, components, and related methods are described. An illumination assembly can include at least one solid state light-emitting device, an emission surface through which light is emitted, and a wavelength converting material that wavelength converts at least some light emitted by the solid state light-emitting device. The wavelength converting material can have a first density per unit area of the emission surface at a first location and a second density per unit area of the emission surface at a second location, wherein the second density is substantially different from the first density, and wherein the density per unit area is defined with a  1×1  cm 2  averaging area. Another illumination assembly can include a light guide configured to receive light emitted by a solid state light-emitting device. The light guide can have a length along which received light propagates and an emission surface substantially parallel to the length of the light guide and through which light is emitted. A wavelength converting material can have a density per unit area of the emission surface that substantially increases along the length of the light guide.

FIELD

The present embodiments are drawn generally towards illuminationsystems, and more specifically, illumination systems including solidstate light-emitting devices.

BACKGROUND

Illumination assemblies can provide light for a variety of applications,including general lighting and electronic applications. For example, abacklighting assembly can be used to provide light for a display, suchas a liquid crystal display (LCD). Currently such backlightingassemblies mainly employ cold cathode fluorescent tubes (CCFLs) lightsources. Although these fluorescent tubes can provide efficientdistributed lighting, serious disadvantages of fluorescent tubes includecomplicated inverter electronics, slow switching speeds, and thepresence of hazardous materials, such as mercury, within the fluorescenttubes.

SUMMARY

Illumination systems, components, and methods associated therewith areprovided.

In one aspect, an illumination assembly comprises at least one solidstate light-emitting device, an emission surface through which light isemitted, and a wavelength converting material that wavelength convertsat least some light emitted by the solid state light-emitting device,the wavelength converting material having a first density per unit areaof the emission surface at a first location and a second density perunit area of the emission surface at a second location, wherein thesecond density is substantially different from the first density, andwherein the density per unit area is defined with a 1×1 cm² averagingarea.

In another aspect, an illumination assembly comprises a solid statelight-emitting device, a light guide configured to receive light emittedby the solid state light-emitting device, the light guide having alength along which received light propagates and an emission surfacesubstantially parallel to the length of the light guide and throughwhich light is emitted, and a wavelength converting material having adensity per unit area of the emission surface that substantiallyincreases along the length of the light guide.

In one aspect, a display comprises at least one solid statelight-emitting device, an emission surface through which light isemitted, a wavelength converting material that wavelength converts atleast some light emitted by the solid state light-emitting device, thewavelength converting material having a first density per unit area ofthe emission surface at a first location and a second density per unitarea of the emission surface at a second location, wherein the seconddensity is substantially different from the first density, and whereinthe density per unit area is defined with a 1×1 cm² averaging area, anda liquid crystal layer arranged to receive at least some wavelengthconverted light emitted by the wavelength converting material.

In one aspect, a display comprises at least one solid statelight-emitting device, a first wavelength converting material regionthat wavelength converts at least some light emitted by the solid statelight-emitting device to a first wavelength spectrum, a secondwavelength converting material region that wavelength converts at leastsome light emitted by the solid state light-emitting device to a secondwavelength spectrum different from the first wavelength spectrum, and aliquid crystal layer comprising a first pixel light valve arranged toreceive at least some wavelength converted light emitted by the firstwavelength converting material, and a second pixel light valve arrangedto receive at least some wavelength converted light emitted by thesecond wavelength converting material.

In one aspect, a method of making an illumination assembly comprisingproviding at least one solid state light-emitting device, and providinga wavelength converting material that wavelength converts at least somelight emitted by the solid state light-emitting device, the wavelengthconverting material having a first density per unit area of an emissionsurface at a first location and a second density per unit area of theemission surface at a second location, wherein the second density issubstantially different from the first density, and wherein the densityper unit area is defined with a 1×1 cm² averaging area.

Other aspects, embodiments and features of the invention will becomeapparent from the following detailed description of the invention whenconsidered in conjunction with the accompanying figures. Theaccompanying figures are schematic and are not intended to be drawn toscale. Each identical or substantially similar component that isillustrated in various figures is represented by a single numeral ornotation.

For purposes of clarity, not every component is labeled in every figure.Nor is every component of each embodiment of the invention shown whereillustration is not necessary to allow those of ordinary skill in theart to understand the invention. All patent applications and patentsincorporated herein by reference are incorporated by reference in theirentirety. In case of conflict, the present specification, includingdefinitions, will control.

BRIEF DESCRIPTION OF FIGURES

FIG. 1A is a perspective view of an illumination assembly including awavelength converting material, in accordance with one embodiment;

FIG. 1B is a cross-section view of an illumination assembly including atapered extraction region, in accordance with one embodiment;

FIG. 1C is a cross-section view of a display including an illuminationassembly as a backlight unit, in accordance with one embodiment;

FIGS. 2A-B are flowcharts of methods for wavelength converting andspatially homogenizing light, in accordance with one embodiment;

FIG. 3A is a cross-section view of an illumination assembly having aspatially varying density of a wavelength converting material, inaccordance with one embodiment;

FIG. 3B is a chart of a density of wavelength converting material versusdistance from a light source, in accordance with one embodiment;

FIG. 4 is a cross-section view of an illumination assembly having aspatially varying density of a wavelength converting material due to adiffering microscopic density of the wavelength converting material, inaccordance with one embodiment;

FIG. 5 is a cross-section view of an illumination assembly having aspatially varying density of a wavelength converting material due to adiffering thickness of a wavelength converting material layer, inaccordance with one embodiment;

FIG. 6 is a top view of an illumination assembly having a spatiallyvarying density of a wavelength converting material due to a differingspatial arrangement of a plurality of wavelength converting materialregions, in accordance with one embodiment;

FIG. 7 is a top view of an illumination assembly having spatiallyvarying density of a wavelength converting due to a differing size of aplurality of wavelength converting material regions, in accordance withone embodiment;

FIGS. 8A-B are cross-section and top views, respectively, of anillumination assembly including wavelength converting material over alight emission surface of a light guide, in accordance with oneembodiment;

FIG. 9 is a cross-section view of an illumination assembly includingwavelength converting material under a backside surface of a lightguide, in accordance with one embodiment;

FIG. 10 is a cross-section view of an illumination assembly includingwavelength converting material over a light emission surface of a lightguide, in accordance with one embodiment;

FIG. 11A is a top view of an illumination assembly including a pluralityof wavelength converting material regions, in accordance with oneembodiment;

FIG. 11B is a top view of an illumination assembly including a pluralityof wavelength converting material regions, in accordance with oneembodiment;

FIGS. 12A-B are cross-section and top views, respectively, of anillumination assembly including a wavelength converting material, inaccordance with one embodiment;

FIG. 13 is a top view of an illumination assembly including a wavelengthconverting material, in accordance with one embodiment;

FIGS. 14A-B are cross-section and top views, respectively, of anillumination assembly including a wavelength converting material and oneor more wavelength filters, in accordance with one embodiment;

FIGS. 15A-B are cross-section and top views, respectively, of anillumination assembly including a wavelength converting material, inaccordance with one embodiment; and

FIG. 16 is a perspective view of a solid state light-emitting device, inaccordance with one embodiment.

DETAILED DESCRIPTION

Illumination assemblies presented herein can include one or more solidstate light-emitting devices, such as light-emitting diodes and/or laserdiodes. These solid state light-emitting devices can serve as highbrightness compact light sources for a variety of applications. Sincesolid state light-emitting devices are typically compact light sources,for applications where distributed lighting is desired, light emitted bythe solid state light-emitting devices can be incorporated into anillumination assembly that can redirect and emit light via an extendedlight emission surface having a surface area substantially greater thanthe emission surface of the light-emitting devices (e.g., greater thanabout 100 times, greater than about 500 times, greater than about 1000times, greater than about 2000 times). Some embodiments presented hereincan accomplish such redirection and emission of light from one or moresolid state light-emitting devices and can provide for distributedillumination via an extended light emission surface. In someembodiments, during the process of light redirection and/or emission,some or all of the light from the light-emitting devices may bewavelength converted. Wavelength conversion of some or all of the lightcan facilitate redirection and/or emission of the light from theillumination assembly.

Some embodiments presented herein include illumination assemblies withone or more solid state light-emitting devices that can emit primarylight having a first wavelength spectrum and a wavelength convertingmaterial (e.g., phosphors and/or quantum dots) that can covert theprimary light to secondary light having a different wavelength spectrum(e.g., down-convert the primary light to a lower energy). As usedherein, a wavelength converting material refers to a material that canabsorb some or substantially all of the primary light having a firstwavelength spectrum (e.g., blue light, UV light) and emit secondarylight having a second different wavelength spectrum (e.g., white light,yellow light, red light, green light, and/or blue light). The wavelengthconverting material can down-convert light from shorter wavelengths(higher energies) to longer wavelengths (shorter energies). Phosphorsare examples of typical wavelength converting materials, which can takethe form of phosphor particles. Quantum dots can also serve aswavelength converting materials.

In some embodiments presented herein, the wavelength converting materialcan have a density that differs in different locations. The density ofwavelength converting material per unit area is the amount of wavelengthconverting material per averaging area disposed above and underneath anaveraging area of 1×1 cm². For example, in some embodiments, theaveraging area can be located on the emission surface of an illuminationassembly, and in such cases, the density is referred to as the densityof wavelength converting material per unit area of the emission surface.Such an averaging area excludes variations of wavelength convertingmaterial density at the package level of a solid state light-emittingdevice, for example, variations of wavelength converting materialdensity within an encapsulant layer of a light-emitting device.

FIG. 1A illustrates an illumination assembly including one or more solidstate light-emitting devices, in accordance with one embodiment.Illumination assembly 100 a can include a solid state light-emittingdevice 150 which may include one or more light-emitting diodes and/orlaser diodes. Although the illumination assembly illustrated in FIG. 1Ais edge-lit by one or more solid state light-emitting devices,alternatively or additionally, an illumination assembly can be back-litby one or more solid sate light-emitting devices. In some embodiments, aplurality of illumination assemblies, similar to illumination assembly100 a, can be arranged adjacent each other (e.g., tiled along either oneor two dimensions) to form a combined illumination assembly having acombined light emission surface (e.g., adjacent light emission surfacesthat can tile a surface, such as a plane). The light emission surfacearea of an illumination assembly (or combined assembly) may be greaterthan about 0.01 m² (e.g., greater than or equal to about 0.05 m²,greater than or equal to about 0.1 m², greater than or equal to about0.16 m², greater than or equal to about 0.5 m², greater than or equal toabout 1 m²). In some embodiments, the light emission surface area of anillumination assembly ranges between about 0.01 m² and about 0.05 m²,between about 0.05 m² and about 0.1 m², between about 0.1 m² and about0.5 m², or between about 0.5 m² and about 1 m².

Light 152 (referred to as primary light) emitted by the light-emittingdevice 150 may be coupled into a light homogenization region 112 thatcan spatially distribute the light such that light emitted via a lightoutput boundary 113 (e.g., light output surface) has a substantiallyuniform intensity on different locations of the light output boundary113. Light homogenization region 112 may be a region where light is notsubstantially extracted along the length of the homogenization region112.

Light homogenization region 112 may comprise a light guide having ahigher index than a surrounding medium. The light guide can include anedge configured to receive the light emitted by the solid statelight-emitting device 150. For example, light homogenization region 112may include part or all of a light guide formed of an opticallytransparent material such as transparent plastic (e.g., PMMA, acrylic)and/or glass. The light guide can have any suitable shape. In someembodiments, the light guide has a slab shape (e.g., rectangular slab,square slab, trapezoidal slab), a cylindrical shape (e.g., rod with acircular or elliptical cross-section), and/or other suitable lightguiding shapes. The shape of the light output boundary of thehomogenization region may be related to the shape of the light guide,for example, a rectangular light guide including a homogenization regionmay be such that the light output boundary is a rectangularcross-section of the rectangular guide, as illustrated in FIG. 1A.

Light 153 outputted by the light homogenization region 112 may becoupled to a light extraction region 114 where light is substantiallyextracted along the light extraction region 114. Light extraction region114 can include a light emission surface 120 through which light 102 canbe emitted. The emission surface of the light extraction region may besubstantially perpendicular to the general direction of the light 153inputted into the light extraction region 114. Light extraction region114 can include light scattering features that can scatter light out viathe light emission surface 120. In some embodiments, light extractionregion 114 can be configured and arranged such that light emission formemission surface 120 has a substantially uniform (e.g., less than about20% variation, less than about 15% variation, less than about 10%variation) light intensity across the emission surface 120.

Light extraction region 114 may comprise a light guide. Light scatteringfeatures may be located in the light guide volume and/or on the topand/or bottom surfaces of the light guide. The number of scatteringfeatures may vary along the length of the light guide so as to ensurethat light emission via the light emission surface is substantiallyuniform along the length of the light guide. As illustrated in FIG. 1A,the light emission surface 120 can be substantially parallel to thelength of the light guide. In some embodiments, the intensity variationof light emitted along the length of the light guide is less than about20% (e.g., less than about 15%, less than about 10%, less than about5%). In some embodiments, light extraction region 114 may include partor all of a light guide formed of an optically transparent material suchas glass or a plastic material (e.g., acrylic, PMMA).

In some embodiments, a gap 104 may be present between the light outputboundary 113 of homogenization region 112 and the light extractionregion 114. the gap 104 can ensure that any light that is coupled intothe light extraction region 114 remains confined in the light extractionregion due to total internal reflection (e.g., in the absence ofscattering features and/or a light guide tapering). Alternatively,homogenization region 112 and extraction region 114 may be in contactwith each other. For example, homogenization region 112 and extractionregion 114 may both be part of a single light guide.

Illumination assembly 100 a can include wavelength converting materialin one or more locations, such as one or more phosphors and/or one ormore types of quantum dots. The wavelength converting material canabsorb and convert primary light having a first wavelength spectrum tosecondary light having a second wavelength spectrum different from thefirst wavelength spectrum. In some embodiments, the wavelengthconverting material can down-convert light having higher energy (e.g.,shorter wavelengths) to light having lower energy (e.g., longerwavelengths). For example, the wavelength converting material candown-convert blue and/or ultraviolet light to longer wavelength light,such as red, green, yellow, or blue light, or combinations thereof.White light can be created with a combination of multiple colors, forexample, blue and yellow, or blue, green, and red. Thus, one method offorming white light using a wavelength converting material can includedown-converting some blue primary light to yellow and forming whitelight with a combination of secondary yellow light and unconvertedprimary blue light. Another method of forming white light includesdown-converting some primary blue light to red and green light, forexample using two or more different wavelength converting materials(e.g., a red-emitting and a green-emitting wavelength convertingmaterial). Another method of forming white light includesdown-converting ultraviolet light to red, green, and blue light, forexample using two or more different wavelength converting materials(e.g., a red-emitting, a green-emitting, and a blue-emitting wavelengthconverting material).

In some embodiments, wavelength converting material is disposed withinhomogenization region 112. Alternatively, or additionally, wavelengthconverting material may be disposed within extraction region 114. Thepresence of wavelength converting material in the illumination assemblycan facilitate the process of spatial homogenization and/or extractionof light from the illumination assembly (e.g., via the light emissionsurface 120).

The wavelength converting material may be located within part or all ofthe homogenization region 112 such that some or all of the primary lightfrom light-emitting device 150 may be wavelength converted within thehomogenization region 112. The process of wavelength conversion canfacilitate light homogenization since primary light 152 traveling in agiven direction based on the arrangement of the light-emitting device150 can be absorbed by the wavelength converting material and secondarylight can be re-emitted in any other direction with equal probability.This can also allow for a decrease in the length of the homogenizationregion used to provide for a substantially uniform light intensity atlight output boundary 113. The placement of the wavelength convertingmaterial in the homogenization region 112 can provide for the output ofsecondary light from the homogenization region 112, or a combination ofsecondary and primary light.

In some embodiments, the wavelength converting material may be uniformlydistributed throughout the light homogenization region 112. In otherembodiments, the wavelength converting material may have a varyingdensity for at least two locations in the homogenization region 112. Forexample, the density of wavelength converting material can be highest atthe light output boundary 113. Alternatively, the density of wavelengthconverting material can be lowest at the light output boundary 113. Thewavelength converting material density may be graded and may vary (e.g.,decrease or increase) as a function of distance from the light outputboundary (or equivalently, as a function of distance from the lightsource).

One or more different wavelength converting materials can be included inthe illumination assembly. In some embodiments, the wavelengthconverting material includes a first wavelength converting material thatcan emit secondary light having a first dominant wavelength and a secondwavelength converting material that can emit secondary light having asecond dominant wavelength different from the first dominant wavelength.The first wavelength converting material can be disposed in the opticalpath between the solid state light-emitting device and the secondwavelength converting material. The first dominant wavelength can belarger than the second dominant wavelength. In other embodiments, thefirst dominant wavelength can be smaller than the second dominantwavelength. A wavelength filter can be disposed in the optical pathbetween the first and the second wavelength converting materials, andconfigured to reflect light emitted by the second wavelength convertingmaterial and transmit light emitted by the first wavelength material andthe solid state light-emitting device.

Alternatively, or additionally, wavelength converting material may belocated within part or throughout all of the light extraction region114. Primary light traveling within light extraction region 114 can thusbe wavelength converted and secondary light can be generated andextracted via emission surface 120. Primary light traveling through thelight extraction region 114 can also be scattered by wavelengthconverting material within the light extraction region 114 and some ofthe primary light can thus be extracted via emission surface 120 by sucha mechanism. Light outputted by the illumination assembly can includeboth some primary light and secondary light. Alternatively, the lightoutputted by the illumination assembly may include secondary light withno primary light. In some embodiments, the light outputted by theillumination assembly is white light, which may be formed by thecombination of primary light (e.g., blue light) and secondary light(e.g., yellow light). Alternatively, the light outputted by theillumination assembly is white light including the secondary light andnot including any substantial amount of primary light (e.g., UV light).

FIG. 1B is a cross-section view of an illumination assembly 100 bincluding a tapered extraction region 114, in accordance with oneembodiment. The taper can be provided by a wedge-shaped light guide. Thelight guide can include an edge configured to receive the light emittedby the solid state light-emitting device. A tapered extraction region114 can facilitate light extraction via the frustration of totalinternal reflection in the light guide. Such a mechanism can be usedalone, or in combination with light scattering features (e.g., surfacefeatures such as prisms and/or lens, volume features such as regionswith different refractive indices than the surrounding light guidematerial), to provide for light extraction via light emission surface120.

It should be appreciated that illumination assemblies can include one ormore reflectors. A backside reflector can be disposed under the backsidesurface (e.g., opposite the light emission surface 120) of the lightextraction region and can reflect back any light that is scattereddownwards (e.g., by light extraction features). That reflected light canthen be extracted via light emission surface 120.

In some embodiments, an illumination assembly can serve as a backlightunit for a display, such as a LCD. Such an embodiment is illustrated inthe cross-section schematic of FIG. 1C. One or more layers 190 of thedisplay 100 c may be illuminated by the illumination assembly. Layer(s)190 may include a liquid crystal light valve layer (corresponding to theliquid crystal light-valve pixels of the display) located over lightemission surface 120. The illumination assembly can thus serve as abacklighting assembly for the liquid crystal display layer and light 102from the illumination assembly can impinge on the liquid crystal displaylayer.

Other layers often used in LCDs, such as diffuser layers, brightnessenhancement films (BEFs), and/or color filters may be located over thelight emission surface of the illumination assembly. In addition todisplay backlighting, the illumination assembly can be used forillumination purposes, including but not limited to, signagebacklighting, outdoor lighting, indoor lighting, automotive lighting,and other lighting applications. For a general lighting assembly, theillumination assembly can be used as is or may have other layersdisposed over the emission surface of the assembly, for example one ormore layers may be located over the assembly so as to alter thelightening character. For example, a textured or patterned layer oroptic (e.g., a polymer and/or glass component) may be placed over theassembly.

In some embodiments, a liquid crystal display system can include a smallnumber of high light output power light-emitting devices that provideillumination for a large display area. Such a liquid crystal display caninclude a liquid crystal display panel having an illumination area, andat least one sold state light-emitting device associated with the liquidcrystal display panel such that light emitted from the solid statelight-emitting device illuminates the liquid crystal display panel. Thedisplay can include a wavelength converting material located remotely(e.g., in a light homogenization region 112 and/or a light extractionregion 114) from solid state light-emitting device. In some embodiments,the number of solid state light-emitting device per m² of theillumination area is less than 100, as discussed further below.

In some embodiments, a small number of high light output powerlight-emitting devices can be used to illuminate a large emission areaof an illumination assembly (e.g., an LCD backlighting assembly). Insome embodiments, the number of light-emitting devices per unit area ofthe emission surface of an illumination assembly is less than or equalto about 300 per m² (e.g., less than or equal to about 200 per m², lessthan or equal to about 100 per m², less than or equal to about 50 perm², less than or equal to about 25 per m², less than or equal to about12 per m²). For example, the number of light-emitting devices per m² ofthe emission surface of an illumination assembly may be between 5 to100, between 25 to 100, or between 50 to 100. A small number oflight-emitting devices per unit area can be enabled by the use ofhigh-power light-emitting devices which can be designed to emit asubstantial amount of their generated light via a large die surface area(e.g., greater than about 4 mm², greater than about 10 mm², greater thanabout 30 mm², greater than about 100 mm²), as discussed further below.

The number of light-emitting devices per illumination assembly may beless than or equal to 12 (e.g., less than or equal to about 8, less thanor equal to about 6, less than or equal to about 4, less than or equalto about 2). In some embodiments, a single light-emitting device mayilluminate an entire illumination assembly.

The total number of light-emitting devices for certain illuminationassemblies has been provided above. For numbering purposes, each of thefollowing may count as one light-emitting device: a light-emitting die,two or more associated light-emitting dies, a partially packagedlight-emitting die or dies, or a fully packaged light-emitting die ordies. For example, one light-emitting device may include a redlight-emitting die associated with a green light-emitting die andassociated with a blue light-emitting die.

In some embodiments, a light-emitting device is a light-emitting devicethat emits light of a single color. For example, the light-emittingdevice may be a red, green, blue, yellow, and/or cyan light-emittingdevice. In other embodiments, the light-emitting device is amulti-colored light-emitting device that emits light having a spectrumof wavelengths. For example, the light-emitting device may be ared-green-blue light-emitting device. In other embodiments, thelight-emitting device may be a red-green-blue-yellow light-emittingdevice. In yet other embodiments, the light-emitting device may be ared-green-blue-cyan light-emitting device. In yet other embodiments, thelight-emitting device is a red-green-blue-cyan-yellow light-emittingdevice. Illumination assemblies can also include combinations oflight-emitting device types such as the ones described above. Of course,light-emitting devices of different colors can also be used inembodiments.

Illumination assemblies such as those illustrated herein can be used toperform light homogenization and/or light extraction. FIG. 2Aillustrates a flowchart 200 a of a method for homogenizing andwavelength converting light simultaneously, in accordance with oneembodiment. The method can be performed by an illumination assembly thatcan include a wavelength converting material in a light homogenizationregion, such as the illumination assemblies illustrated in FIGS. 1A-C.The method can begin with the production of primary light (act 202 a).The primary light may be generated by a solid state light-emittingdevice, such as one or more light-emitting diodes and/or laser diodes.

The primary light may then be spatially homogenized and some orsubstantially all of the primary light may be wavelength converted tosecondary light (act 204 a). The wavelength conversion may be performedby wavelength converting material, such as one or more phosphors and/orone or more types of quantum dots. Since the process of wavelengthconversion can involve the absorption of primary light by the wavelengthconverting material and the emission of secondary light (e.g.,down-converted to lower energies) with any direction of emission havingan equal probability, spatial homogenization can be accomplished usingshorter homogenization lengths that without the use of a wavelengthconverting material. The method can proceed with the extraction of thesecondary light and optionally also some or all of any unconvertedprimary light (act 206 a). Light extraction may occur via a lightemission surface of a light extraction region of an illuminationassembly. The light emission surface may be a surface of a light guide,such as a top face of a slab light guide, as previously described. Insome embodiments, wavelength conversion occurs only within thehomogenization region and not within the light extraction region.

FIG. 2B illustrates a flowchart 200 b of a method for wavelengthconverting and extracting light simultaneously, in accordance with oneembodiment. The method can be performed by an illumination assembly thatcan include a wavelength converting material in an extraction region,such as the illumination assemblies illustrated in FIGS. 1A-C. Themethod can begin with the production of primary light (act 202 b). Theprimary light may be generated by a solid state light-emitting device,such as one or more light-emitting diodes and/or laser diodes. Theprimary light may then be spatially homogenized (act 204 b).

The method can proceed with the simultaneous wavelength conversion of atleast some of the primary light to secondary light and extraction of thesecondary light and optionally also some or all of any unconvertedprimary light. The wavelength conversion may be performed by wavelengthconverting material, such as one or more phosphors and/or one or moretypes of quantum dots. In some embodiments, the wavelength convertingmaterial (e.g., phosphor particles and/or quantum dots) can absorb someprimary light impinging thereon and/or scatter some light (e.g., primaryor secondary light) impinging thereon. The process of wavelengthconversion can involve the absorption of primary light by the wavelengthconverting material and the emission of secondary light (e.g.,down-converted to lower energies) with any direction of emission havingan equal probability. Also, some primary light that impinges onwavelength converting material within the light extraction region may bescattered and thereby extracted. Therefore, the wavelength convertingmaterial can perform both wavelength conversion and light scattering.The method can proceed with the extraction of some or all of thesecondary light and optionally some or all of any unconverted primarylight (act 206 a). Light extraction may occur via a light emissionsurface of a light extraction region of an illumination assembly. Thelight emission surface may be a surface of a light guide, such as a topface of a slab light guide. In some embodiments, wavelength conversionoccurs only within the light extraction region and not within the lighthomogenization region.

FIG. 3A is a cross-section view of an illumination assembly 300 having adifferent density of a wavelength converting material for at least twolocations, in accordance with one embodiment. By arranging thewavelength converting material with a density that differs in differentlocations, the percentage of primary light that is wavelength convertedto secondary light at various locations can be different. Spatialvariation in the percentage of primary light that is wavelengthconverted at different locations can be used to output light with adesired intensity at different locations of a light emission surface120. For example, the wavelength converting material density can behigher in locations where the primary light intensity is lower (ascompared to locations with a higher primary light intensity). Such aconfiguration may be used to compensate for the spatial variation ofprimary light intensity along the light extraction region 114 such thatthe amount of secondary light generated and outputted at differentlocations along the light emission surface 120 is substantially uniform.Furthermore, the wavelength converting material can serve as lightscattering features that can scatter primary light out via the emissionsurface 120, therefore the spatial variation of the wavelengthconverting material density may also allow for the primary lightoutputted from the light emission surface 120 to be substantiallyuniform over the entire surface.

The density of wavelength converting material per unit area of the lightemission surface 120 may vary substantially (e.g., at least 30%variation, at least 60% variation, at least 100% variation) at differentlocations. For example, the density of the wavelength convertingmaterial per unit area of the light emission surface may vary as afunction of distance from the solid state light-emitting device 150. Thedensity of the wavelength converting material can vary at differentlocations of the light extraction region 114. Alternatively, oradditionally, the density of the wavelength converting material can varyat different locations of the light homogenization region 112. Forexample, locations 172 and 174 of FIG. 3A represent two opposing ends ofthe light extraction region 114 at which the wavelength convertingmaterial density per unit emission area can differ.

In some embodiments, the density of the wavelength converting materialcan substantially increase (e.g., monotonically) further away from thesolid state light source, such as the solid state light-emitting device150. In some embodiments, the density of the wavelength convertingmaterial is such that at locations further away from the solid statelight-emitting device 150, the density is substantially greater (e.g.,greater than about 30%, greater than about 60%, greater than about 100%)than that at locations closer to the solid state light-emitting device150.

FIG. 3B is a plot of the density of wavelength converting materialversus distance from a light source, in accordance with one embodiment.Curve 101 represents the wavelength converting material density (e.g.,per unit volume, area, or length) as a function of distance from thelight source, where in the illustrated plot the wavelength convertingmaterial density increases with distance from the solid statelight-emitting device 150.

For the illustrated example, the variation of the wavelength convertingmaterial density can be expressed in terms of the distance along thelight extraction region 114. For example, the left-most portion of curve101 may be associated with the density at location 172 of the lightextraction region 114 and the right-most portion of the curve 101 may beassociated with the density at location 174 of the light extractionregion 114.

In some embodiments, the wavelength converting material density can belower in locations illuminated with a higher intensity of light (e.g.,primary light) from the solid state light-emitting device 150 than inlocations illuminated with a lower intensity of light (e.g., primarylight) from the solid state light-emitting device 150. For illuminationassemblies having a plurality of solid state light-emitting devices, thewavelength converting material can have a lower density in locationsilluminated with a higher intensity of light (e.g., primary light) fromthe plurality of solid state light-emitting devices than in locationsilluminated with a lower intensity of light (e.g., primary light) fromthe plurality of solid state light-emitting devices.

In some embodiments, a spatial variation of the density of wavelengthconverting material can be used to facilitate spatially uniform lightemission across the light emission surface 120 of the light extractionregion 114. The intensity of the secondary light and/or primary lightemitted and/or scattered by the wavelength converting material can varyby less than about 20% (e.g., less than about 15%, less than about 10%,less than 5%) across the light extraction region 114. For example, inthe case of a variation of light intensity of less than about 10% acrossthe light extraction region, a first density at a first location and asecond density at a second location of the light extraction region 114can be such that the wavelength converted light intensity (e.g.,secondary light intensity) from the first location is at least about 90%the wavelength converted light intensity (e.g., secondary lightintensity) from the second location and no greater than about 110% thewavelength converted light intensity from the second location. In someembodiments, the density can vary inversely with the primary lightintensity at different locations along the light extraction region 114.For example, the second density can be greater than or equal to about 2times (e.g., greater than or equal to about 3 times, greater than orequal to about 4 times) the first density, which can compensate forapproximately a 50% reduction in primary light intensity so as toproduce substantially the same intensity of secondary light at the firstand second locations along the light extraction region 114. As should beappreciated, the first and second locations can be opposing ends of alight extraction region 114 (e.g., locations 172 and 174), however theembodiments are not limited in this respect.

FIG. 4 is a cross-section view of an illumination assembly 400 having adifferent density of a wavelength converting material (e.g., per unitarea over an averaging area of 1×1 cm² on the emission surface 120) forat least two locations due to a differing microscopic density of thewavelength converting material, in accordance with one embodiment. Afirst location 172 can have a first density of wavelength convertingmaterial 117 and a second location 174 can have a second density ofwavelength converting material 117. The second density can besubstantially different from the first density at least partially due toa differing microscopic density of wavelength converting material at thefirst and second locations. As described herein, the wavelengthconverting material can include one or more phosphors and/or quantumdots, and the microscopic density can be the number of phosphormolecules and/or quantum dots per unit volume over a length-scale muchsmaller than the averaging length-scale used to calculate the density(e.g., much smaller than an averaging area of 1×1 cm²). As illustratedin FIG. 4, wavelength converting material 117 can be dispersedthroughout the light extraction region 114 or on portions of the lightextraction region 114. In some embodiments, the wavelength convertingmaterial 117 microscopic density can vary (e.g., increase monotonically,decreases monotonically) along the length of the light extraction region114.

FIG. 5 is a cross-section view of an illumination assembly 500 having adifferent density of a wavelength converting material (e.g., per unitarea over an averaging area of 1×1 cm² on the emission surface 120) forat least two locations due to a differing thickness of a wavelengthconverting material region, in accordance with one embodiment. Thewavelength converting material region 116 can include a wavelengthconverting material layer that can comprise wavelength convertingmaterial (e.g., phosphor and/or quantum dot particles) in a hostmaterial (e.g., polymer, glass). The density of wavelength convertingmaterial per unit area of the light emission surface 120 at a firstlocation 172 may be substantially different from the density at a secondlocation 174 at least partially due to a differing thickness of thewavelength converting material region 116 at the first location 172 andsecond location 174. In some embodiments, the wavelength convertingmaterial region 116 (e.g., layer) can be part of the light extractionregion 114. When a light extraction region 114 includes a light guide110, the wavelength converting material region 116 (e.g., layer) may bedisposed over the light guide 110 (e.g., on light emission surface 121of the light guide 110), disposed under the light guide 110 (e.g., on abackside opposing the light emission surface 121 of the light guide),and/or embedded in the light guide 110.

Other ways of varying the density of wavelength converting material(e.g., per unit area over an averaging area of 1×1 cm² on the emissionsurface 120) are possible. For example, in some embodiments, thewavelength converting material can be part of a plurality of wavelengthconverting material regions (e.g., each region having a size of lessthan about 50 microns, less than about 100 microns, or less than about500 microns) and the density of the wavelength converting material(e.g., per unit area over an averaging area of 1×1 cm² on the emissionsurface 120) can vary from one location to another at least partiallydue to a differing spatial arrangement and/or size of the plurality ofwavelength converting material regions. In some embodiments, thewavelength converting material regions include dots, squares,rectangles, triangles, hexagons, stripes, and/or any other shapes thatcan include wavelength converting material (e.g., dispersed in and/or ona host material).

FIG. 6 is a top view of an illumination assembly 600 having a differentdensity (e.g., per unit area over an averaging area of 1×1 cm² on theemission surface 120) of a wavelength converting material for at leasttwo locations due to a differing spatial arrangement of a plurality ofwavelength converting material regions 116, in accordance with oneembodiment. The wavelength converting material regions 116 can comprisewavelength converting material (e.g., phosphor and/or quantum dotparticles) in a host material (e.g., polymer, glass).

In the illustrated illumination assembly 600, the wavelength convertingmaterial regions 116 can be dots, squares, stripes, and/or any othersuitable shapes. The plurality of wavelength converting material regions116 can have substantially similar shapes. The wavelength convertingmaterial regions 116 can be arranged spatially so as to have differentnearest neighbor distances as a function of location along the lightextraction region 114. In some embodiments, the wavelength convertingmaterial regions 116 can be arranged in a periodic or non-periodicpattern. Examples of such patterns are described in further detailbelow.

FIG. 7 is a top view of an illumination assembly 700 having a differentdensity of a wavelength converting material for at least two locationsdue to a differing size of a plurality of wavelength converting materialregions 116, in accordance with one embodiment. As illustrated, the sizeof the wavelength converting material regions 116 can vary with locationalong the light extraction region 114 (e.g., as a function of distancefrom the light-emitting device 150), and the spatial arrangement (of thecenters) of the wavelength converting material regions 116 can be thesame for all locations. It should be appreciated that the density ofwavelength converting material (e.g., per unit area over an averagingarea of 1×1 cm² on the emission surface 120) can be different indifferent locations due to one or more of the aforementioned reasonsand/or other reasons.

FIGS. 8A-B are cross-section and top views, respectively, of anillumination assembly 800 including wavelength converting materialdisposed over a light emission surface 121 of a light guide 110, inaccordance with one embodiment. The light guide 110 can be configured toreceive light 152 emitted by the solid state light-emitting device 150.Light guide 110 can include an edge 122 configured to receive light 152emitted by the solid state light-emitting device 150. The light guide110 can include a length along which received light propagates. Aspreviously described, light from the light-emitting device 150 may bespatially homogenized in light homogenization region 112. Homogenizedlight may be coupled into the light extraction region 114.

Light guide 110 can include a light emission surface 121. In someembodiments, wavelength converting material regions 116 may be disposedover the light emission surface 121 of the light guide 110. It should beappreciated that since the wavelength converting material regions 116can emit secondary light (e.g., wavelength converted light) andpotentially scatter primary light that impinges on the wavelengthconverting material features 116, both the wavelength convertingmaterial regions 116 and the light guide 110 can be considered to bepart of the light extraction region 114 of the illumination assembly800. Therefore the light emission surface of the illumination assembly800 can comprise the exposed surfaces of the wavelength convertingmaterial features 116 and the exposed surface of the light guide 110.

Light coupled into the extraction region 114 may travel and remainconfined within light guide 110 in part or completely due to totalinternal reflection off of the surfaces of the light guide 110.Alternatively, or additionally, light confinement within the light guide110 may be due to reflective regions disposed in contact with at least aportion of the light guide 110 surfaces. For example, reflective layer126 may be located over the edge of the light guide 110 opposing thelight input edge 122. A reflector 124 may be disposed under the backsidesurface of the light guide 110. Reflective layers may be directly incontact with the light guide or may be separated from the light guide bya gap. Reflective layers may be formed of any suitable material,including but not limited to a reflective metal (e.g., aluminum, silver,and/or combinations thereof), and may be specular and/or diffusereflectors.

Light traveling within the extraction region 114 may be emitted due to afrustration of total internal reflection which may be due to lightscattering due to light scattering features 118 (e.g., convex lens,concave lens, convex prisms, concave prisms, refractive indexvariations), a tapering of the light guide thickness along the length ofthe guide (not shown), scattering of primary or secondary light due tointeraction with wavelength converting material in regions 116, and/oremission of wavelength converted light (e.g., secondary light) bywavelength converting material in regions 116. In some embodiments, thescattering of primary light can be solely due to interaction with thewavelength converting material and no light scattering features 118 needbe present. In some embodiments, scattering features 118 may be presenton the backside surface and/or emission surface 121 of the light guide.

In some embodiments, the wavelength converting material may have avarying density per unit area of the emission surface along the lengthof the light guide. In some embodiments, the wavelength convertingmaterial has a density per unit area of the emission surface thatsubstantially increases along the length of the light guide. Density canthus generally increase along the length of the light guide, howeverthere may exist minor variations about the generally increasing densitytrend.

Wavelength converting material features 116 may have any desired shapes(e.g., stripes, dots, squares) and may be arranged in with varyingnearest neighbor distances along the length of the light guide 110. Inthe illustrated illumination assembly shown in FIGS. 8A-B, thewavelength converting region(s) 116 take the form of stripes and can bespaced closer to each other further away from the light-emitting device150. The wavelength converting material regions 116 may include a layerat least partially or completely disposed over the emission surface ofthe light guide 110. The wavelength converting material regions 116 maybe partially (or completely) disposed in contact with the light emissionsurface 121 of the light guide 110. Alternatively, or additionally,wavelength converting material may be disposed within and/or under thelight guide.

The density of the wavelength converting material per unit area of theemission surface can vary monotonically with distance along the lengthof the light guide (e.g., related to distance from the light-emittingdevice). The density of wavelength converting material per unit area ofthe emission surface can vary at least partially due to a varyingdensity of wavelength converting material, a varying thickness, avarying spatial arrangement and/or size of a plurality of wavelengthconverting material regions 116, as previously described. In theillustrated assembly of FIGS. 8A-B, the density varies along the lengthof the light guide due to a varying distance between wavelengthconverting material regions 116 (e.g., distance between strips thatinclude wavelength converting material).

Illumination assembly 800 may include one or more wavelength filters.The wavelength filters may be reflective filters that can reflect lightin some range of wavelengths and transmit light with wavelengths outsidethe range, and/or the wavelength filter may be absorptive filters thatcan absorb light in some range of wavelengths and transmit light withwavelengths outside the range. The wavelength filters may includeshort-pass, long-pass filters, or combinations thereof.

In some embodiments, a wavelength filter may be disposed in the opticalpath between the solid sate light-emitting device and the wavelengthconverting material. This filter may prevent any wavelength convertedlight from entering the light-emitting device or escaping via theexposed region of the light input edge. For example, illuminationassembly 800 may include a wavelength filter 129 arranged over the inputedge 122 of the light guide 110. Wavelength filter 129 may be configuredto allow primary light (e.g., blue and/or UV light) emitted by the lightemitted device 150 to be transmitted, and to reflect secondary light(e.g., down-converted light) emitted by the wavelength convertingmaterial in regions 116. Thus, wavelength filter 129 may preventsecondary light from escaping the light guide 110 via edge 122.

In some embodiments, a wavelength filter may be disposed in the opticalpath between the wavelength converting material and the before theoutput of the illumination assembly. This filter may prevent any primarylight from escaping the illumination assembly and may be particularlyuseful when the primary light is UV light. Illumination assembly 800 mayinclude such a wavelength filter 128 which may be disposed over theemission surface of the light extraction region 114.

In some embodiments, light 102 emitted by the illumination assembly 800can include a mixture of secondary and primary light. In otherembodiments, light 102 emitted by the illumination assembly 800 caninclude substantially only secondary light. For example, if wavelengthfilter 128 is absent, light 102 emitted by the illumination assembly mayinclude a combination of primary and secondary light (e.g., white lightformed from a combination of various wavelengths, such as blue andyellow light, or blue, green and red light).

FIG. 9 is a cross-section view of an illumination assembly 900 includingwavelength converting material disposed under a backside surface of alight guide 110, in accordance with one embodiment. In the illustratedillumination assembly 900, light extraction features may be absent. Thelight guide 110 can include a backside surface opposing the lightemission surface 121 of the light guide 110, and wavelength convertingmaterial regions 116 may be partially (or completely) disposed under thebackside surface. The wavelength converting material regions 116 can bepartially (or completely) disposed in contact with the backside surfaceof the light guide 110. Alternatively, or additionally, the wavelengthconverting material may be disposed within the light guide 110. Thewavelength converting material regions 116 may be disposed in contactwith backside reflector 124, which can aid in the extraction of any heatgenerated by the wavelength converting material. Backside reflector 124may be thermally coupled to a heat sink to provide for heat dissipation.

FIG. 10 is a cross-section view of an illumination assembly 1000including wavelength converting material disposed over a light emissionsurface 121 of a light guide 110, in accordance with one embodiment. Awavelength filter 132 may be disposed between the light emission surface121 of the light guide 110 and wavelength converting material regions116. Wavelength filter 132 may be configured to transmit primary lightand reflect secondary light emitted by the wavelength convertingmaterial. Thus, wavelength filter 132 may reflect secondary light thatis emitted by the wavelength converting material in regions 116 so as toprevent the secondary light from entering the light guide 110.

FIG. 11A is a top view of an illumination assembly 1100 a including aplurality of wavelength converting material regions 116, in accordancewith one embodiment. The wavelength converting material regions 116 maybe arranged with a varying nearest neighbor distance at differentlocations along a light guide 110, thereby providing for a varyingdensity of wavelength converting material along the light extractionregion 114. The wavelength converting material regions 116 may have anyshape, for example, the regions may comprise dots, as illustrated inFIG. 11A. Additionally or alternatively, the thickness and/or size ofthe wavelength converting material regions 116 may vary in differentlocations of the light extraction region 114. For example, the regions116 may be thicker closer to the light-emitting device 150.

FIG. 11B is a top view of an illumination assembly 1100 b including awavelength converting material, in accordance with one embodiment.Illumination assembly 1100 b can include a plurality of wavelengthconverting material regions (e.g., dots 116 a-c) that can be arranged soas to aligned with and disposed over a plurality of display pixel lightvalves (of a liquid crystal layer) so as to individually illuminate thepixel light valves. For example, the display pixel light valves may bepart of a liquid crystal layer (not shown for clarity) placed over theemission surface 121 of the illumination assembly 1100 b, as previouslyillustrated and described in FIG. IC. The size of each wavelengthconverting material region (e.g., dots 116 a-c) can be about the size ofthe display pixel light-valves.

Different wavelength converting materials (e.g., red-emitting phosphor,green-emitting phosphor, blue-emitting phosphor) can be located indifferent wavelength converting material regions (e.g., dots 116 a-c)such that different pixel light valves can be illuminated with adifferent color of light. Such assemblies can allow for the eliminationof color filters in LCDs and can thus improve the LCD system efficiency.In some such assemblies, the light-emitting devices can emit UV primarylight which can be converted by different wavelength convertingmaterials in different regions (e.g., dots). In some such assemblies,the light-emitting devices can emit blue primary light. When blueprimary light is used, red-emitting and green-emitting wavelengthconverting materials can be used to illuminate red and green pixel lightvalves, respectively, whereas blue pixel light valves can be illuminatedby the primary light (e.g., which can be extracted locally using lightscattering features of the light guide 110 aligned with the blue pixellight valves).

FIGS. 12A-B are cross-section and top views, respectively, of anillumination assembly 1200 including wavelength converting materialhaving a spatially varying density (e.g., per unit area over anaveraging area of 1×1 cm² on the emission surface of the assembly), inaccordance with one embodiment. A plurality of light-emitting devices150 can be arranged to emit light into one or more edges of the lightguide 110. The wavelength converting material density (e.g., per unitarea over an averaging area of 1×1 cm² on the emission surface of theassembly) can vary in one or two dimensions. FIG. 12B illustrates anembodiment where the spatial variation of the wavelength convertingmaterial density per unit area can vary in two dimensions that definethe emission surface 121.

The density of the wavelength converting material per unit area can beconfigured so as be higher in portions of the light guide 110 where theprimary light intensity is lower. For example, when the primary lightintensity is lower in the center portion 181 and the corner portions 182of the light guide 110, the wavelength converting material may have ahigher density (as illustrated by the darker shaded portions of the topview in FIG. 12B) in those portions of the light guide 110. Such aninverse relationship can allow for compensation of decreased primarylight intensity along the light guide 110 such that light 102 emitted bythe illumination assembly can be substantially spatially uniform acrossthe entire emission surface 121.

FIG. 13 is a top view of an illumination assembly 1300 including awavelength converting material having a spatially varying density (e.g.,per unit area over an averaging area of 1×1 cm² on the emissionsurface), in accordance with one embodiment. Illumination assembly 1300is similar to illumination assembly 1200, except that the plurality oflight-emitting devices 150 can emit light into the corner portions oflight guide. Such an arrangement can allow for a more spatially uniformprimary light intensity within the light guide 110, as compared to theassembly 1200 of FIG. 12. In turn, for circumstances where a spatiallyuniform light emission is desired from the illumination assembly, thewavelength converting material density per unit area need only have ahigher value in the center portion 181 of the light guide. In someembodiments, a portion or all of the edges of the light guide (notcoupling light from light-emitting devices 150) may be coated with areflective material (e.g., a metal such as aluminum and/or silver) so asto prevent any light (e.g., primary and/or secondary light) fromescaping the light guide.

FIGS. 14A-B are cross-section and top views, respectively, of anillumination assembly 1400 including a wavelength converting materialand one or more wavelength filters, in accordance with one embodiment.

Illumination assembly 1400 can include one or more solid statelight-emitting devices 150. A light guide 110 can be configured toreceive primary light 152 emitted by the solid state light-emittingdevice 150, where the light guide 110 can have a length along whichlight propagates and an emission surface 121 through which light isemitted. A wavelength converting material that can generate secondarylight 153 can be disposed in the optical path between the solid statelight-emitting device 150 and the emission surface 121 of the lightguide.

One or more wavelength filter(s) (e.g., filter 129) can be disposed inthe optical path between the solid sate light-emitting device 150 andthe wavelength converting material. The wavelength filter 129 can beconfigured to transmit primary light emitted by the light-emittingdevice 150 and reflect secondary light (e.g., wavelength convertedlight). Thus, wavelength filter 129 can comprise a short pass wavelengthfilter disposed over (e.g., directly on) the light input side 122 of thelight homogenization region, wherein the short pass wavelength filter isconfigured to transmit light from the solid state light-emitting device150 and reflect wavelength converted light from the wavelengthconverting material. Wavelength filter 129 can thus prevent wavelengthconverted light that is back-emitted or back-scattered from escaping thehomogenization region 112.

Illumination assembly 1400 can include light homogenization region 112disposed in the optical path between the solid state light-emittingdevice 150 and the emission surface 121 of the light guide 110. Thewavelength converting material may be disposed within the lighthomogenization region 112. As used herein, the term “disposed within”means located inside the homogenization region and not located at theinput or output edges of the homogenization region.

The wavelength converting material can be disposed within at least aportion of the homogenization region 112 or throughout the entirehomogenization region 112. Alternatively, or additionally, thewavelength converting material can be located at one or more edges ofthe light homogenization region, for example on the light input edge 122and/or the light output edge 113 of the homogenization region. In someembodiments, the density of the wavelength converting material can varyat different locations in the homogenization region 112. For example,the density of the wavelength converting material may be higher furtheraway from the light input edge 122.

In some embodiments, illumination assembly 1400 can include wavelengthfilter 128 (e.g., a long pass wavelength filter) on a light output sideof the light homogenization region 112. Wavelength filter 128 can beconfigured to transmit the wavelength converted light (e.g., secondarylight) from the wavelength converting material and reflect primary lightemitted by the solid state light-emitting device 150.

Multiple wavelength filters can be arranged in a cascadingconfiguration, where the light output of one wavelength filter can serveas the light input of another wavelength filter. Wavelength convertingmaterial can be disposed in the optical path between the light outputside of one wavelength filter and the light input side of anotherwavelength filter. The wavelength converting material can be different(e.g., wavelength convert different wavelength ranges and/or generatedifferent wavelengths of secondary light) in different regions. Forexample, different wavelength converting materials can be cascaded inthe optical path. In some embodiments, lower energy (e.g., longerwavelength) light can be generated by a wavelength converting materialcloser to the light-emitting device 150 and successfully higher energylight (e.g., shorter wavelength) can be generated by one or moredifferent wavelength converting materials arranged in successionthereafter. In other embodiments, high energy (e.g., shorter wavelength)light can be generated by a wavelength converting material closer to thelight-emitting device 150 and successfully lower energy light (e.g.,longer wavelength) can be generated by one or more different wavelengthconverting materials arranged in succession thereafter.

Different wavelength converting materials can be isolated from anotherby one or more wavelength filters. The wavelength filter(s) can beconfigured to prevent secondary light from a given wavelength convertingmaterial from entering a different wavelength converting materiallocated closer to the light-emitting device 150. For example, theillumination assembly 1400 can comprise a second short pass wavelengthfilter (in addition to wavelength filter 129) and a second wavelengthconverting material different from the first wavelength convertingmaterial. The second short pass filter can be disposed in the opticalpath between the wavelength converting material and the secondwavelength converting material, and the second short pass wavelengthfilter can be configured to transmit light from the solid statelight-emitting device, transmit wavelength converted light from thewavelength converting material, and reflect wavelength converted lightfrom the second wavelength converting material.

In some embodiments, illumination assembly 1400 can include one or morereflective surfaces 125 on one or more surfaces and/or edges of thelight homogenization region 114. The reflective surfaces 125 can preventlight (e.g., primary and/or secondary light) from escaping via edgesand/or surfaces of the homogenization region 112. Thus, in such anembodiment, light can essentially be outputted only from the lightoutput edge 113 of the light homogenization region and not via otheredges or surfaces of the light homogenization region 112.

FIGS. 15A-B are cross-section and top views, respectively, of anillumination assembly 1500 including a backlight wavelength convertingregion 116, in accordance with one embodiment. Illumination assembly1500 can include one or more light-emitting devices 150 including lightemission surfaces 38. The wavelength converting material 116 can bedisposed over the light emission surfaces 38 of the solid statelight-emitting devices 150. Thus, in such an arrangement, thelight-emitting devices 150 can directly backlight the wavelengthconverting material 116 with primary light 152 emitted by thelight-emitting devices 150.

The one or more solid state light-emitting devices 150 can be located ona first plane. In one embodiment, the solid state light-emitting devices150 are supported by a thermal management system, which can include aheat conductive plane 159 (e.g., a metal planar layer). The wavelengthconverting material 116 can be disposed over the emission surfaces ofthe light-emitting devices 150 and, in some instances, may be arrangedon a second plane substantially parallel to the first plane on which thelight-emitting devices 150 can be arranged.

In one embodiment, the wavelength converting material 116 can have adensity per unit area that is different at different locations (e.g., atdifferent locations of the second plane). For example, first and secondlocations of the wavelength converting material 116 may be located atdifferent locations of the second plane parallel to the first plane onewhich the light-emitting devices 150 can be located. The first locationsmay be disposed over the light emission surfaces 38 of thelight-emitting devices 150 and second locations may be disposed overregions in-between the light emission surfaces 38 of the light-emittingdevices 150. The density of wavelength converting material in the firstregions may be lower than the density of wavelength converting materialin the second regions. Such an arrangement can compensate for a lowerprimary light intensity at regions in-between the light-emitting devices150 (e.g., not directly above a light-emitting device 150 emission area38) so as to provide for substantially similar secondary light intensityacross the entire emission surface of the illumination assembly (e.g.,the second plane). Generally, in some embodiments, the wavelengthconverting material 116 can have a lower density per unit area inlocations illuminated with a higher intensity of primary light than inlocations illuminated with a lower intensity of primary.

In some embodiments, the illumination assembly 1500 can include one ormore wavelength filters. Wavelength filter 129 may be disposed betweenthe light-emitting devices 150 and the wavelength converting material116. Wavelength filter 129 may include a short pass filter configured totransmit primary light from the light-emitting devices and reflectsecondary light generated by the wavelength converting material inregion 116. In some embodiments, wavelength filter 128 may be disposedover the emission surface of the wavelength converting material 116.Wavelength filter 128 may include a long pass filter configured totransmit secondary light generated by the wavelength converting materialin region 116 and reflect primary light emitted by the light-emittingdevices 150. Such an arrangement can be beneficial when the primarylight is ultra-violet light and the secondary light is visible light. Inthese arrangement, it may be desirable to only output secondary visiblelight (e.g., light 102) and reflect back ultra-violet primary light(e.g., using filter 128) so as not to expose a viewer of theillumination assembly to ultra-violet light. Alternatively, light 102may include a mixture of primary and secondary light, for example amixture of blue primary light and secondary light, such as yellow, red,and/or green light. Such arrangements can be used to generate whitelight.

Various methods can be employed to make the illumination assembliesdescribed herein. With regards to forming the wavelength convertingmaterial regions, methods such as printing, molding (e.g., injectionmolding), coating, spraying, and/or embossing may be employed. Forexample, a printing process (e.g., a jet printing process) may be usedto create wavelength converting material having a spatially varyingdensity (e.g., per unit area of the emission surface of the illuminationassembly). The printer cartridge may include a solution comprising thewavelength converting material (e.g., phosphor and/or quantum dots).Varying thickness of a wavelength converting material region can then becreated by performing a longer printing step at different locations.Alternatively, or additionally, small features (e.g., dots, stripes)with small sizes (e.g., less than 500 microns, less than 200 microns,less than 100 microns) can be printed with a spatially varying nearestneighbor distance. In other embodiments, wavelength converting materialmay be included in a molding material (e.g., a polymer such as PMMA oracrylic) so as to have a varying density at different locations of themolded component, such as a molded light guide.

In some embodiments, an illumination assembly may include a thermalmanagement system that can dissipate heat produced by the light-emittingdevices. In some embodiments, the thermal management system may belocated on the backside of the illumination assembly (e.g., the sideopposite the light emission surface). Such a feature may be desirablewhen the light-emitting devices are high-power light-emitting devicesthat generate significant amounts of heat, as may be the case when fewlight-emitting devices are used to illuminate each tile. Examples ofthermal management systems for display and illumination systems areprovided in U.S. patent application Ser. No. 11/413,968, entitled “LCDThermal Management Methods and Systems,” filed on Apr. 28, 2006, whichis herein incorporated by reference in its entirety. Generally, athermal management system may include a suitable system that can conductand dissipate heat which may be generated by devices and components ofthe illumination assembly. In some embodiments, a thermal managementsystem may be characterized by, or may include one or more componentsthat are characterized by, a thermal conductivity greater than 5,000W/mK, greater than 10,000 W/mK, and/or greater than 20,000 W/mK. In someembodiments, the thermal conductivity lies in a range between 10,000W/mK and 50,000 W/mK (e.g., between 10,000 W/mK and 20,000 W/mK, between20,000 W/mK and 30,000 W/mK, between 30,000 W/mK and 40,000 W/mK,between 40,000 W/mK and 50,000 W/mK).

In some embodiments, a thermal management system can include passiveand/or active heat exchanging mechanisms. Passive thermal managementsystems can include structures formed of one or more materials thatrapidly conduct heat as a result of temperature differences in thestructure. Thermal management systems may also include one or moreprotrusions which can increase the surface contact area with thesurrounding ambient and therefore facilitate heat exchange with theambient. In some embodiments, a protrusion may include a fin structurethat may have a large surface area. In a further embodiment, a thermalmanagement system can include channels in which fluid (e.g., liquidand/or gas) may flow so as to aid in heat extraction and transmission.For example, the thermal management system may comprise one or more heatpipes to facilitate heat removal. Various heat pipes are well known tothose in the art, and it should be understood that the embodimentspresented herein are not limited to merely to such examples of heatpipes. Heat pipes can be designed to have any suitable shape, and arenot necessarily limited to only cylindrical shapes. Other heat pipeshapes may include rectangular shapes which may have any desireddimensions. In some embodiments, one or more heat pipes may be arrangedsuch that a first end of the heat pipes is located in regions of theillumination assembly that are exposed to high temperatures, such as inproximity to one or more light-emitting devices. A second end of theheat pipes (i.e., a cooling end) may be exposed to the ambient. The heatpipes may be in thermal contact with protrusions to aid in heat exchangewith the ambient by providing increased surface area. Since heat pipesmay have a thermal conductivity that is many times greater (e.g., 5times greater, 10 times greater) than the thermal conductivity of manymetals (e.g., copper), the conduction of heat may be improved via theincorporation of the heat pipes into illumination systems.

Active thermal management systems may include one or more suitable meansthat can further aid in the extraction and transmission of heat. Suchactive thermal management systems can include mechanical, electrical,chemical and/or any other suitable means to facilitate the exchange ofheat. In one embodiment, an active thermal management system may includea fan used to circulate air and therefore provide cooling. In anotherembodiment, a pump may be used to circulate a fluid (e.g., liquid, gas)within channels in the thermal management system. In furtherembodiments, the thermal management system may include a thermalelectric cooler that may further facilitate heat extraction.

In some embodiments, the solid state light-emitting devices in theillumination assemblies presented herein can include a light-emittingdiode. FIG. 16 illustrates a light-emitting diode (LED) which may be oneexample of a light-emitting device, in accordance with one embodiment.It should be understood that various embodiments presented herein canalso be applied to other light-emitting devices, such as laser diodes,and LEDs having different structures (such as organic LEDs, alsoreferred to as OLEDs). LED 1600 shown in FIG. 16 comprises a multi-layerstack 31 that may be disposed on a support structure (not shown). Themulti-layer stack 31 can include an active region 34 which is formedbetween n-doped layer(s) 35 and p-doped layer(s) 33. The stack can alsoinclude an electrically conductive layer 32 which may serve as a p-sidecontact, which can also serve as an optically reflective layer. Ann-side contact pad 36 may be disposed on layer 35. Electricallyconductive fingers (not shown) may extend from the contact pad 36 andalong the surface 38, thereby allowing for uniform current injectioninto the LED structure.

It should be appreciated that the LED is not limited to theconfiguration shown in FIG. 16, for example, the n-doped and p-dopedsides may be interchanged so as to form a LED having a p-doped region incontact with the contact pad 36 and an n-doped region in contact withlayer 32. As described further below, electrical potential may beapplied to the contact pads which can result in light generation withinactive region 34 and emission (represented by arrows 152) of at leastsome of the light generated through an emission surface 38. As describedfurther below, holes 39 may be defined in an emission surface to form apattern that can influence light emission characteristics, such as lightextraction and/or light collimation. It should be understood that othermodifications can be made to the representative LED structure presented,and that embodiments are not limited in this respect.

The active region of an LED can include one or more quantum wellssurrounded by barrier layers. The quantum well structure may be definedby a semiconductor material layer (e.g., in a single quantum well), ormore than one semiconductor material layers (e.g., in multiple quantumwells), with a smaller electronic band gap as compared to the barrierlayers. Suitable semiconductor material layers for the quantum wellstructures can include InGaN, AlGaN, GaN and combinations of theselayers (e.g., alternating InGaN/GaN layers, where a GaN layer serves asa barrier layer). In general, LEDs can include an active regioncomprising one or more semiconductors materials, including III-Vsemiconductors (e.g., GaAs, AlGaAs, AlGaP, GaP, GaAsP, InGaAs, InAs,InP, GaN, InGaN, InGaAlP, AlGaN, as well as combinations and alloysthereof), II-VI semiconductors (e.g., ZnSe, CdSe, ZnCdSe, ZnTe, ZnTeSe,ZnS, ZnSSe, as well as combinations and alloys thereof), and/or othersemiconductors. Other light-emitting materials are possible such asquantum dots or organic light-emission layers.

The n-doped layer(s) 35 can include a silicon-doped GaN layer (e.g.,having a thickness of about 4000 nm thick) and/or the p-doped layer(s)33 include a magnesium-doped GaN layer (e.g., having a thickness ofabout 40 nm thick). The electrically conductive layer 32 may be a silverlayer (e.g., having a thickness of about 100 nm), which may also serveas a reflective layer (e.g., that reflects upwards any downwardpropagating light generated by the active region 34). Furthermore,although not shown, other layers may also be included in the LED; forexample, an AlGaN layer may be disposed between the active region 34 andthe p-doped layer(s) 33. It should be understood that compositions otherthan those described herein may also be suitable for the layers of theLED.

As a result of holes 39, the LED can have a dielectric function thatvaries spatially according to a pattern. Typical hole sizes can be lessthan about one micron (e.g., less than about 750 nm, less than about 500nm, less than about 250 nm) and typical nearest neighbor distancesbetween holes can be less than about one micron (e.g., less than about750 nm, less than about 500 nm, less than about 250 nm). Furthermore, asillustrated in the figure, the holes 39 can be non-concentric.

The dielectric function that varies spatially according to a pattern caninfluence the extraction efficiency and/or collimation of light emittedby the LED. In some embodiments, a layer of the LED may have adielectric function that varies spatially according to a pattern. In theillustrative LED 1600, the pattern is formed of holes, but it should beappreciated that the variation of the dielectric function at aninterface need not necessarily result from holes. Any suitable way ofproducing a variation in dielectric function according to a pattern maybe used. For example, the pattern may be formed by varying thecomposition of layer 35 and/or emission surface 38. The pattern may beperiodic (e.g., having a simple repeat cell, or having a complex repeatsuper-cell), or non-periodic. As referred to herein, a complex periodicpattern is a pattern that has more than one feature in each unit cellthat repeats in a periodic fashion. Examples of complex periodicpatterns include honeycomb patterns, honeycomb base patterns, (2×2) basepatterns, ring patterns, and Archimedean patterns. In some embodiments,a complex periodic pattern can have certain holes with one diameter andother holes with a smaller diameter. As referred to herein, anon-periodic pattern is a pattern that has no translational symmetryover a unit cell that has a length that is at least 50 times the peakwavelength of light generated by one or more light-generating portions.As used herein, peak wavelength refers to the wavelength having amaximum light intensity, for example, as measured using aspectroradiometer. Examples of non-periodic patterns include aperiodicpatterns, quasi-crystalline patterns (e.g., quasi-crystal patternshaving 8-fold symmetry), Robinson patterns, and Amman patterns. Anon-periodic pattern can also include a detuned pattern (as described inU.S. Pat. No. 6,831,302 by Erchak, et al., which is incorporated hereinby reference in its entirety). In some embodiments, a device may includea roughened surface. The surface roughness may have, for example, aroot-mean-square (rms) roughness about equal to an average feature sizewhich may be related to the wavelength of the emitted light.

In certain embodiments, an interface of a light-emitting device ispatterned with holes which can form a photonic lattice. Suitable LEDshaving a dielectric function that varies spatially (e.g., a photoniclattice) have been described in, for example, U.S. Pat. No. 6,831,302B2, entitled “Light emitting devices with improved extractionefficiency,” filed on Nov. 26, 2003, which is herein incorporated byreference in its entirety. A high extraction efficiency for an LEDimplies a high power of the emitted light and hence high brightnesswhich may be desirable in various optical systems.

It should also be understood that other patterns are also possible,including a pattern that conforms to a transformation of a precursorpattern according to a mathematical function, including, but not limitedto an angular displacement transformation. The pattern may also includea portion of a transformed pattern, including, but not limited to, apattern that conforms to an angular displacement transformation. Thepattern can also include regions having patterns that are related toeach other by a rotation. A variety of such patterns are described inU.S. Patent Publication No. 20070085098, entitled “Patterned devices andrelated methods,” filed on Mar. 7, 2006, which is herein incorporated byreference in its entirety.

Light may be generated by the LED as follows. The p-side contact layercan be held at a positive potential relative to the n-side contact pad,which causes electrical current to be injected into the LED. As theelectrical current passes through the active region, electrons fromn-doped layer(s) can combine in the active region with holes fromp-doped layer(s), which can cause the active region to generate light.The active region can contain a multitude of point dipole radiationsources that generate light with a spectrum of wavelengthscharacteristic of the material from which the active region is formed.For InGaN/GaN quantum wells, the spectrum of wavelengths of lightgenerated by the light-generating region can have a peak wavelength ofabout 445 nanometers (nm) and a full width at half maximum (FWHM) ofabout 30 nm, which is perceived by human eyes as blue light. The lightemitted by the LED may be influenced by any patterned surface throughwhich light passes, whereby the pattern can be arranged so as toinfluence light extraction and/or collimation.

In other embodiments, the active region can generate light having a peakwavelength corresponding to ultraviolet light (e.g., having a peakwavelength of about 370-390 nm), violet light (e.g., having a peakwavelength of about 390-430 nm), blue light (e.g., having a peakwavelength of about 430-480 nm), cyan light (e.g., having a peakwavelength of about 480-500 nm), green light (e.g., having a peakwavelength of about 500 to 550 nm), yellow-green (e.g., having a peakwavelength of about 550-575 nm), yellow light (e.g., having a peakwavelength of about 575-595 nm), amber light (e.g., having a peakwavelength of about 595-605 nm), orange light (e.g., having a peakwavelength of about 605-620 nm), red light (e.g., having a peakwavelength of about 620-700 nm), and/or infrared light (e.g., having apeak wavelength of about 700-1200 nm).

In certain embodiments, the LED may emit light having a high lightoutput power. As previously described, the high power of emitted lightmay be a result of a pattern that influences the light extractionefficiency of the LED. For example, the light emitted by the LED mayhave a total power greater than 0.5 Watts (e.g., greater than 1 Watt,greater than 5 Watts, or greater than 10 Watts). In some embodiments,the light generated has a total power of less than 100 Watts, thoughthis should not be construed as a limitation of all embodiments. Thetotal power of the light emitted from an LED can be measured by using anintegrating sphere equipped with spectrometer, for example a SLM12 fromSphere Optics Lab Systems. The desired power depends, in part, on theoptical system that the LED is being utilized within. For example, adisplay system (e.g., a LCD system) may benefit from the incorporationof high brightness LEDs which can reduce the total number of LEDs thatare used to illuminate the display system.

The light generated by the LED may also have a high total power flux. Asused herein, the term “total power flux” refers to the total opticalpower divided by the emission area. In some embodiments, the total powerflux is greater than 0.03 Watts/mm², greater than 0.05 Watts/mm²,greater than 0.1 Watts/mm², or greater than 0.2 Watts/mm². However, itshould be understood that the LEDs used in systems and methods presentedherein are not limited to the above-described power and power fluxvalues.

In some embodiments, the LED may be associated with one or morewavelength converting regions. The wavelength converting region(s) mayinclude one or more phosphors and/or quantum dots. The wavelengthconverting region(s) can absorb light emitted by the light-generatingregion of the LED and emit light having a different wavelength than thatabsorbed. In this manner, LEDs can emit light of wavelength(s) (and,thus, color) that may not be readily obtainable from LEDs that do notinclude wavelength converting regions. In some embodiments, one or morewavelength converting regions may be disposed over (e.g., directly on)the emission surface (e.g., surface 38) of the light-emitting device.

As used herein, an LED may be an LED die, a partially packaged LED die,or a fully packaged LED die. It should be understood that an LED mayinclude two or more LED dies associated with one another, for example ared light-emitting LED die, a green light-emitting LED die, a bluelight-emitting LED die, a cyan light-emitting LED die, or a yellowlight-emitting LED die. For example, the two or more associated LED diesmay be mounted on a common package. The two or more LED dies may beassociated such that their respective light emissions may be combined toproduce a desired spectral emission. The two or more LED dies may alsobe electrically associated with one another (e.g., connected to a commonground).

As used herein, when a structure (e.g., layer, region) is referred to asbeing “on”, “over” “overlying” or “supported by” another structure, itcan be directly on the structure, or an intervening structure (e.g.,layer, region) also may be present. A structure that is “directly on” or“in contact with” another structure means that no intervening structureis present.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

1-28. (canceled)
 29. An illumination assembly for a display assembly, the display assembly including a plurality of display pixel light valves, the illumination assembly comprising: a solid-state light-emitting device that outputs a primary light having a primary spectrum; a light guide configured to receive the primary light emitted by the solid-state light-emitting device, the light guide having a length along which the primary light propagates and a light emission surface; and first wavelength converting material regions and second wavelength converting material regions at the emission surface, the first wavelength converting material regions configured to convert the primary light incident thereon to a first converted light having a first converted wavelength spectrum and the second wavelength converting material regions configured to convert the primary light incident thereon to a second converted light having a second converted wavelength spectrum different from the first converted wavelength spectrum, each wavelength converting material region aligned with a respective pixel light valve and having a size approximately equal to a size of the respective pixel light valve so that the first converted light from the first wavelength converting material regions and the second converted light from the second wavelength converting material regions individually illuminate the respective pixel light valves.
 30. The illumination assembly of claim 29, wherein the first converted light has a lower energy than the second converted light, and the second converted light has a lower energy than the primary light.
 31. The illumination assembly of claim 30, wherein: the first wavelength converting material regions comprise a first wavelength converting material that converts the primary light to red light; the second wavelength converting material regions comprise a second wavelength converting material that converts the primary light to green light; each first wavelength converting material region is aligned with a respective red pixel light valve of the display pixel light valves; and each second wavelength converting material region is aligned with a respective green pixel light valve of the display pixel light valves.
 32. The illumination assembly of claim 31, wherein the primary light is blue light, and the illumination assembly further includes light scattering features at the emission surface, the light scattering features aligned with and illuminating blue pixel light valves.
 33. The illumination assembly of claim 29, wherein the primary light is ultraviolet light or blue light.
 34. The illumination assembly of claim 29, additionally comprising third wavelength converting material regions at the emission surface, the third wavelength converting material regions configured to convert the primary light incident thereon to a third converted light having a third converted wavelength spectrum different from the first converted wavelength spectrum and different from the second converted wavelength spectrum, each third wavelength converting material region aligned with a respective pixel light valve and having a size approximately equal to a size of the respective pixel light valve so that the third converted light from the third wavelength converting material regions individually illuminate the respective pixel light valves.
 35. The illumination assembly of claim 34, wherein the first converted light has a lower energy than the second converted light, the second converted light has a lower energy than the third converted light, and the third converted light has a lower energy than the primary light.
 36. The illumination assembly of claim 35, wherein: the first wavelength converting material regions comprise a first wavelength converting material that converts the primary light to red light; the second wavelength converting material regions comprise a second wavelength converting material that converts the primary light to green light; the third wavelength converting material regions comprise a third wavelength converting material that converts the primary light to blue light; each first wavelength converting material region is aligned with a respective red pixel light valve of the display pixel light valves; each second wavelength converting material region is aligned with a respective green pixel light valve of the display pixel light valves; and each third wavelength converting material region is aligned with a respective blue pixel light valve of the display pixel light valves.
 37. The illumination assembly of claim 36, wherein the primary light is ultraviolet light.
 38. The illumination assembly of claim 29, wherein the display pixel light valves are light valves of a liquid crystal display.
 39. The illumination assembly of claim 38, wherein the liquid crystal display does not include color filters.
 40. The illumination assembly of claim 29, wherein at least one of the first wavelength converting material regions or the second wavelength converting material regions comprise quantum dots.
 41. The illumination assembly of claim 29, wherein at least one of the first wavelength converting material regions or and the second wavelength converting material regions comprise a phosphor.
 42. The illumination assembly of claim 29, wherein the solid-state light-emitting device comprises a light-emitting diode.
 43. The illumination assembly of claim 29, wherein the solid-state light-emitting device comprises a laser diode.
 44. The illumination assembly of claim 29, wherein at least some of the wavelength converting material regions are embodied as dots. 